Your contact's Overview screen contains a Memberships section for the contact. Below is an example of this section:
In this section you will see the various types of Membership relationships you've established for your contact within the database.
Clicking Add will allow you to link additional contacts.
Clicking a Linked Contact's name will take you to their record Overview.
Right-clicking an existing membership will present you with the option to edit or remove that membership.
You can view detailed information concerning how to add Memberships here. To learn how to add new Membership options, see this post.